Method of making insulating devices.



R. D. MERSHON. METHOD OF MAKING INSULATING DEVICES.

APPLICATION FILED JAN. 4, 19H). 1,164,739. Patented Dec. 21, 1915.

Fly] my 2 2 4 5, 1 5m a} v 4 {i 5 mm wfoz RALPH D. MERSHON, OF NEW YORK,1\T. Y.

METHOD OF MAKING INSULATING DEVICES.

Specification of Letters Patent.

Patented Dec. 21, 1915.

Application filed January 4, 1910. Serial No. 536,356.

' '1 b all whom it may concern Be it known that .I, RALPH D. MnnsrIoN. a citizen of the United States, residing at New i ork, in the county and State of New York, have invented certain new and useful Improvements in Methods of Making Insulating Devices, of which the following is a full, clear, and exact description.

In the manufacture of large insulating elements of porcelain and analogous materials considerable difiiculty has been eX- perienced in providing the device with suitable flanges or petticoats such as are desired for the purpose of preventing or diminishing leakage of the current over the surface of the insulator. In the case of large pieces it is impracticable, for well understood reasons, to make the petticoats integral with the body of the insulator, and it has therefore been proposed to secure the petticoats to the body or core by means of suitable cement, as for example the glazeslip used to glaze the article, thus making what may for convenience be termed a compound or built-up insulating device. In this method the procedure hitherto has been to dip the petticoats and core or body separately in the slip, assemble the parts, pour more slip between the parts to fill the spaces, and then fire the whole; so that the contiguous coatings of glaze-slip, fusing together, will cement the petticoats to the core. The results attained by this method, however, leave much to be desired. In the first place the amount of slip which can be put into these small spaces, even if they be entirely filled, is not enought to fill. the spaces when the article is fired. This is due to the fact that the slip being in liquid form cannot be poured in so that when dry it will be as dense as the body of the petticoats and core, and consequently when the slip fuses and becomes more dense it does not entirely fill the space. In the second place, the glazeslip will carry with-it more or less air mechanically entrapped and most materials used for the purpose liberate more or less gas or gases in fusing. On a free surface this air and gas can escape and leave a glaze free from bubbles or pits. But in a confined space, such as that in question, the air and gas cannot escape readily and hence produce pockets or cavities in the glazed joint. The result is a defective joint, lacking the mechanical and dielectric strength desired.

The chief object of my present invention is to provide an improved method, of making cemented or glaze-jointed insulating e ments, which shall avoid the defects and disadvantages of the prior methods, such as that outlined above, for example, producing an article in which the joints shall be firm and dense and have the desired mechanical and electric strength. 1

The preferred mode of procedure in carrying out my invention will be described in connection with the accompanying drawing, in which Figure 1 shows the insulating element with the petticoat rings in section. Fig. 2 is a modification.

In the device illustrated in Fig. 1 the petticoats 1 are in the form of rings, and the core or body 2 is a cylinder, which may be solid or hollow as desired, the parts mentioned being made of porcelain or equivalent material. 7

In carrying out my process in the preferred manner the petticoats and core are made of such size that before being glazeslipped they will just go togethermaking a close fit. They are, however, separately coated with glaze-slip, after which the parts will of course not fit together, on account of the coating covering each. I next fire the core alone, with the result that when the core comes from the kiln it has shrunk all it can shrink and has on it a firm clear coat of glaze free from bubbles. This shrinkage of the core reduces its size sufiiciently to allow the petticoats, with their coating of glaze slip dried, to fit easily or loosely over it, after which the assembled article is fired. In the latter step the glaze-slip on the petticoats will melt on account of its relatively low melting temperature, thus freeing it of bubbles, before the petticoats themselves have begun to shrink or have shrunk to any material extent, and the previously fired glaze on the core will also melt. Now as the firing proceeds the petticoats shrink down upon the core and the two dense coatings or melted glaze are thus squeezed together, forming a completely filled, uniform joint, without bubbles, flaws, or cavities. It will be seen that if too much slip is used, making the coatings too thick, full shrinkage of the petticoats may be prevented and the resulting stress may cause them to crack or break. Care should therefore be exercised to have just the amount of glaze necessary to fill the joint. As it may at time be impracticable to exercise such extreme care the necessity therefor may be eliminated by providing suitable recesses in the surface of the core or petticoats, or both, or at the ends of the petticoats, into which the excess of glaze may be squeezed as the petticoats shrink. These ipcesses may take the form of shallow grooves, say on the core, as shown at 3, or they may be formed by beveling the ends of the petticoats more or less, as shown at 4-. Both methods may be used if desired. As stated, the shrinkage of the petticoats squeezes the excess glaze into these spaces,

leaving a firm, homogeneous joint between the core and the petticoats. If desired, slip may be poured between the parts, before firing, but the results will ordinarily not be so good as in the former case since there will be more chance for the formation of bubbles.

Instead of first firing the core separately, as above described, the same results may be secured by the equivalent plan of making the petticoats of material which will have greater shrinkage in firing than the core, or will shrink at a later stage of the firing. In this case the greater or later shrinkage of the petticoats will bring them down upon the shrinking or shrunken core, with the result of bringing the coatings of melted slip firmly together as before described. Argillaceous compositions having different coefficients of shrinkage, that is, compositions which will shrink at different rates during the firing or at different stages of the firing, are well known in the ceramic arts and hence need not be described herein. It will be observed that in the'method in which the core isfired before the petticoats are applied, after which the whole device is fired, the core has in the second firing a shrinkage coefficient of zero, or substantially zero, and that therefore the petticoats and the core have different coefiicients of shrinkage.

The invention may also be used in making elements of types other than that shown in Fig. 1, as for example one composed of sections each formed with one or more integral petticoats. Fig. 2, in which the sections are designated by 5. Here the convex bottom of one section or part fits into the correspondingly concave top of the adjoining section below, the parts being slipped and fired before assembling and then fired after assembling. Recesses for taking care of the excess glaze, as for example the grooves 6, may be provided if found necessary or desirable. In a device of the kind shown in Fig. 2 the surfaces coated with melted glaze are pressed together, as in the former case, but the pressure is the result of gravity rather than shrinkage of the parts.

The mode of procedure herein specifically Such a structure is shown in described is simple and thoroughly effective for the purpose in hand, but-the invention may be practised in other Ways without departure from its proper spirit and scope.

In the appended claims I ,have used the word porcelain'in a generic sense, to cover not only porcelain itself but also similar materials and argillaceous materials generally.

I claim:

1. The method of making insulating devices of porcelain or similar material, comprising forming the device in parts having different coefiicients of shrinkage, covering with glaze the surfaces which are to be joined, assembling the parts, and then firing the device, whereby to melt the glaze and cause the contiguous glazed surfaces to be pressed together by shrinkage during firing.

2. The method of making insulating devices of porcelain, comprising forming a core and firing the same, coating with glazeslip one or more unfired parts and fitting the coated part or parts on the fired core,

and firing the whole, whereby shrinkage of the said part or parts in firing will bring the glaze-coated surface or surfaces thereof into close contact with the core.

3. The method of making insulating devices built up of parts composed of porcelain, comprising coating a core with glazeslip and firing the same, coating with slip one or more unfired parts and then fitting the same on the fired core, and firing the whole, whereby the shrinkage of the said part or parts in the firing will bring the glaze-coated surface or surfaces thereof into close contact with the adjoining glazed surface of the core.

4. The method of making insulating devices built up of parts composed of porcelain, comprising coating a suitable core or body with glaze-slip and firing the same, coating with glaze-slip one or more ringshaped unfired parts and fitting the same around the fired core, and firing the whole, whereby the shrinkage of the ring-shaped part or parts in the firing will bring the glaze-coated surface or surfaces thereof into close contact with the adjoining glazed surface of the core.

5. The method of making petticoated insulating devices composed of porcelain, comprising coating a cylindrical core with glaze-slip and firing the same, coating with glaze-slip a series of ring-shaped petticoat members and fitting the same on the fired core, and firing the whole, whereby the shrinkage of the petticoat members in the firing will bring the glaze-coated surfaces thereof into close contact with the glazed core.

6. The method of making insulating devices of porcelain, comprising forming the having recesses to receive excess glaze during the parts with glaze, and firing the 1S ing firing, coating the parts with glaze, fitwhole. ting the parts together, and firing the whole. In testimony whereof I affix my signature 7. The method of making insulating dein the presence of two subscribing Witnesses.

vices of porcelain, comprisin formin the device in parts shaped to fit together and RALPH MERSHON' having recesses to receive excess glaze dur- Witnesses:

ing firing, said recesses being Wholly Wit1h- M. LAWSON DYER,

in the contiguous surfaces of the parts. coat- S. S. DUNHAM. 

